Many of the biopolymer degrading hydrolytic enzymes, such as cellulases, hemicellulases, ligninases and pectinases have received attention because of their potential applications in food, feed, textile, and pulp and paper industries. Industrial filamentous fungi production strains, in particular Aspergillus and Trichoderma strains, can produce high amounts of extracellular enzymes. These fungi are easy and inexpensive to grow in large bioreactors and they possess good secretion capacity capable of carrying out similar type of protein modifications as occurs in many higher eukaryotes. The existence of hypersecreting strains and strong promoters, such as cellulase promoters, make filamentous fungi hosts also potential for heterologous protein production.
It is known that the production of cellulases, hemicellulases, ligninases and pectinases are mainly regulated at the transcriptional level in filamentous fungi (Aro et al. FEMS Microbiology Reviews 29 (2005) 719-739). Stricker et al. Appl. Microbiol. Biotechnol. (2208) 78:211-220 have described the similarities and differences in the transcriptional regulation of expression of hemicellulases and cellulases in Aspergillus niger and Hypocrea jecorina (T. reesei), including the action of XlnR and Xyr1. In Hypocrea jecorina some regulatory components function in cellulase regulation positively (XYRI, ACE2, HAP2/3/5) and some negatively (ACEI, CREI) (Kubicek et al. Biotechnology and Biofuels 2009, 2:19; Nakari-Setälä et al. Appl and Environmental Microbiology, July 2009, p. 4853-4860).
Although the action of some regulatory genes on the production of cellulases and hemicellulases has been disclosed in the prior art, there is still a need for improved strains capable of enhanced or altered production of cellulases or hemicellulases or other hydrolytic enzymes in filamentous fungi.